The fifth biennial Gordon Research Conference on Mammary Gland Biology will be held 18-22 June, 1979, at Holderness School, Plymouth, N.H. These conferences bring together scientists of many disciplines, all of whom share a major research interest in the mammary gland and whose research interests are broadly diversified. Conferences have been held in alternating years since 1971 and the attendance for these conferences has been: 1971, 50; 1973, 81; 1975, 76; and 1977, 123. It should be noted that the large increase in attendance from 1975 to 1977 probably reflects the continued interest in the need for a multi-disciplinary approach in mammary gland research, and a strong desire of the scientific community to relate this information to the problem of breast cancer. Indeed, the inclusion of sessions devoted to exciting new developments in the field of mammary cancer has fostered the enthusiastic interactions of the attendees. On the basis of the interest expressed to date, we anticipate an attendance of 100 to 125 participants in 1979.